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University of New Mexico (2019)

Fungi in a hot, dry, changing world

Hutchinson Miriam I.

Titre : Fungi in a hot, dry, changing world

Auteur : Hutchinson Miriam I.

Université de soutenance : University of New Mexico

Grade : Doctor of Philosophy in Biology 2019

My doctoral work focused on understanding the reciprocal relationship between fungi and their environment, namely how fungi respond to environmental flux, as well as how fungi can modify and structure their habitats, especially in the context of climate change. As such, I aimed my research on fungi with distinct adaptations to their environmental niches : endophytic fungi that inhabit plant tissue and thermophilic fungi that are capable of growing at the upper temperature limit for eukaryotic life. My research consisted of three studies. First, I investigated the thermophilic species Myceliophthora heterothallica to demonstrate its use as a model organism for efficient cellulose decomposition by identifying its optimal growth and reproductive conditions, as well as the genes involved in mating. In experiments, M. heterothallica proved to be a tractable organism for genetic manipulation as it was easily grown and successfully mutagenized, and strains could be readily crossed. Sequencing of genomes for several strains of M. heterothallica as well as related species led to the discovery that the structure of the mating-type region of heterothallic (outcrossing) species is atypical when compared to related groups in the same order. Although thermophilic fungi are well understood in applied science, their ecology is still unclear. Therefore, in a second study I surveyed a transect in western North America, spanning from Mexico in Canada, in attempts to define the biogeography of fungal thermophiles. Using culture-based methods, I found that thermophilic fungi can be isolated from a variety of substrates and from diverse habitats. Similar to results from previous studies, there was little specificity to their distribution, but the frequency of recovery showed a reciprocal relationship with latitude. For my final study, I conducted a survey on a more local scale at the Sevilleta National Wildlife Refuge. I collected roots from creosote (Larrea tridentata) and black grama (Bouteloua eriopoda) in order to assess the composition of root endophyte populations in these dominant desert plants and to understand what impact shrub encroachment may have on the abundance of different fungi. Using next-generation sequencing, I characterized the communities of root-associated fungi of these plants within a shrub encroachment zone where creosote is expanding into black grama grassland. Fungal root communities were shaped by the host plant as well as the year of collection. The most abundant members of the community included unclassified fungi related to common pathogens, dark-septate endophytes and, notably, a thermophilic spe


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